1. Field of the Invention
The present invention relates to the mechanical field, and especially relates to mechanical equipment.
2. Description of Related Art
The motor is equipment that converts electrical energy into mechanical energy. In various motors, the most widely used is the asynchronous motor. It is easy to use, reliable operation, low prices and solid structure. The asynchronous motor widely applies in the industrial, the agricultural production, the transportation, the defense and the commerce.
In the motion mechanism using the asynchronous motor as the power source, as shown in FIG. 1, the power system of the motion mechanism is mainly constituted by an asynchronous motor 11 and a speed reducer 12. The asynchronous motor 11 and the speed reducer 12 provide power so that the speed reducer 12 drives a transmission belt 13. In the motion process, when it reaches a specified motion stroke, it is usually required to control the asynchronous motor 11 to stop working for stopping the motion of the transmission belt 13.
The control principle is mainly mounting a sensor 16 respectively at an initial position 14 of the motion stroke of the transmission belt 13 and an end position 15. A sensed object 17 is the mounted on the transmission belt 13 to move as the motion of the transmission belt 13. And the sensed object 17 is located between the initial position 14 and the end position 15 of the motion stroke. When the sensed object 17 reaches one of the sensors 16, the sensor 16 senses the sensed object 17 and sends a sensing signal to a control device 18 in order to stop the motion of the transmission belt 13 so that actual motion stroke of the transmission belt 13 would not exceed a predetermined motion stroke.
Through the above way, it can realize the control of the asynchronous motor 11. However, the sensors 16 at the initial position 14 and the end position 15 become essential elements, and they are mounted outside the power system. During equipment maintenance, the maintenance man may touch accidentally the sensors 16 or damage the sensors 16. Therefore, the sensors 16 do not work and cause the failure of the equipment.